The invention relates to semiconductor manufacturing, and more particularly, to methods and systems for transport system (TS) integration.
A typical semiconductor fabrication flow for individual products is a highly re-entrant process. Each product flow requires the same equipment resource many times before completion of its production cycle. A conventional semiconductor factory typically includes fabrication tools for various semiconductor wafer processes, such as, photolithography, chemical-mechanical polishing, or chemical vapor deposition. During manufacture, the semiconductor wafer passes through a series of process steps performed by various fabrication tools. For example, in the production of an integrated semiconductor product, the semiconductor wafer passes through up to 600 process steps.
The wafers are typically stored in containers, such as cassettes, each of which holds up to 25 wafers. The cassettes are then loaded into carriers, such as standard mechanical interfaces (SMIFs) or front opening unified pods (FOUPs) for transport throughout the factory. In a 300 mm fab, an automated material handling system (AMHS) is employed to move carriers containing wafer lots from one location to another based on instructions from the MES. Wafer carriers are typically input to the AMHS using automated equipment. Automated equipment is also used to remove wafer carriers using the fabrication tool loadport as the exit point, with the AMHS and/or removal equipment designed to allow several wafer carriers to accumulate near locations while preventing collisions between adjacent wafer carriers.
A manufacturing execution system (MES) connects to the AMHS and follows a series of standard procedural steps to issue commands to an AMHS, and the AMHS accordingly performs particular transport operations, such as movement of wafer carriers from one location to another, and the like, or replies with information, such as stock information in a particular location, and the like. Several AMHSs are typically installed in different fabrication factories. Conventionally, one MES directs a single AMHS, thus, more MESs are required to serve different AMHSs, resulting in increased cost.